U.S. patent application Ser. No. 14/642,370 discloses a system for selecting an individual (ex.—target, subject) to follow (ex.—track) via an unmanned aerial vehicle (UAV) (ex.—drone, quadcopter) using an onboard camera to capture images. One or more image streams (e.g., a streaming video feed) may be generated from the incoming images and transmitted to external viewers or to a smartphone or other mobile device carried by the subject individual. Image processing and subject tracking systems aboard the UAV may extract image elements from the captured images. For example, incoming images may be analyzed to identify the subject as opposed to his/her surroundings, such as natural features or manmade landmarks, and the position of the UAV relative to the subject interpolated based on the subject's relationship to these features or landmarks. The subject's relative size, position, or orientation (compared to features or landmarks of known position or size, or compared to reference images depicting the subject) may inform the interpolation and determine changes in the position, heading, or velocity of the UAV necessary to maintain a predetermined orientation relative to the moving subject (e.g., 5 meters above and behind the subject's eye level) and thus follow the subject along a path or course, capturing images from a consistent perspective.
U.S. patent application Ser. No. 14/802,871 further discloses a system in which the UAV establishes a wireless link with the subject's smartphone or device, and a GNSS receiver or other position sensor of the device periodically “timestamps” the subject's position, associating a determined position with a fixed time. These timestamps may then be used to reunite the UAV and the subject in the event contact between the two is broken (i.e., visual contact is lost or the wireless link degrades). In both cases, the UAV (i.e., the rotors and motors responsible for propulsion or hovering) and its subsystems may be powered by onboard batteries or similar power supplies. These onboard power supplies may be required to power multiple components from a finite source. It may therefore be desirable for an unmanned aerial vehicle to manage power distribution among multiple components and subsystems, monitoring available power and prioritizing essential systems (i.e., maintaining the UAV inflight) when available power runs low. It may additionally be desirable for the UAV to safely land the UAV if power levels become critical. It may further be desirable to alert the subject if power levels become low or a critical landing is necessary.